MagCheck
27
5.4
Electrode resistance with empty pipe
Low resistance of electrodes with empty pipe may influence accuracy. This may be caused by
humidity on terminal boards in converter and flowhead, defective signal cables at separate meters or
electrode leakage. With empty, clean and dry pipe the electrode resistance must be > 10 MOhms.
The MagCheck limit of > 6 MOhms considers minor insulation degradation on signal cable and
lining.
•
Check converter signal cable connectors, flowhead
terminals and PC-board. Clean, dry?
•
Bottom side of PC-board in flowhead connection box
and connector. Clean and dry thoroughly!
Disconnect signal wires at flowhead terminals 2, 3.
•
Do not disconnect cable shield terminals 1, GND
•
Make sure that open cable ends are clean, dry and do
not contact each other or any flow meter part.
•
Repeat verification. MagCheck result now:
→
NOT OK?
Signal cable
defective,
low insulation
Exchange!
↓
OK?
→
NOT OK?
•
Cable is ok. Investigate flowhead connection box:
Terminals and PC-board clean, dry?
(also: check bottom side and connector)
•
Clean and dry thoroughly! Assemble again.
•
Disconnect all cables to converter
•
Do insulation test on flowhead terminals:
•
Terminal 2 to 1 or GND (
≤
100 VDC).
•
Terminal 3 to 1 or GND (
≤
100 VDC).
Take meter out.
Clean liner.
Remove deposits.
Dry liner.
Repeat insulation
tests on terminals
2, 3 to 1 / GND
↓
↓
↓
OK?
←
←
OK?
→
NOT
OK?
↓
Resistance electrodes with empty pipe OK
Test coil insulation as below/
Contact KROHNE.
